SALIVARY SECRETION IN CATTLE TICK AS A MEANS OF WATER ELIMINATION

In Boophilus microplus and probably other Ixo-didae the blood meal is concentrated, and electrolytic and osmotic im-balance avoided by a remarkable adaptation of the salivary secretion. The effect of host haemoglobin levels on the degree of concentration of the blood ingested by the cattle tick is interesting and may be signifi- cant in the feeding of other blood-sucking arthropods. The general similarity in the proportion of water eliminated from the blood meals of different bloodfeeders, despite their different metabolic and ecologi-cal requirements, may be significant also. It perhaps indicates that this phenomenon is controlled by physical factors which limit the ability of water to leave the blood mass and cross the gut epithelium.